Any Alternatives To Radioactive Treatment For 4th Stage Thyroid Cancer

Hi, my dad s diagnosed with 4th stage thyroid cancer, with metastases to his left pelvic bone & slight traces on the lungs. He has already undergone radioactive iodine treatment 5 times(starting from Feb 2012 every six months) where he is crossed the dosage of 950 mci. He also took thyrogen injection the last two times along with the radioactive iodine treatment. The doctor says that he cannot undergo further radioactive iodine treatment as the maximum dosage is given & more treatment could be toxic for his own body. If the treatment is stopped, won t his cancer spread further? Is there any other alternative to control the cancer? His thyroglobulin blood serum was 18,800 ng/ml 2 years back where the normal range is supposed to be between 1.4-78.0 ng/ml. His recent thryoglobulin blood serum which was taken on 12th Feb 2014 now has reduced to 10,119 ng/ml. Please advise. Thanks & Regards, SRF